1. Field of the Invention
The present invention disclosed in the specification relates to a semiconductor thin film which is formed on a substrate having an insulating surface and a semiconductor device having the semiconductor thin film as an activation layer. Particularly, the present invention relates to a constitution in the case where a crystal silicon film (crystalline silicon film) is used as a semiconductor thin film.
Incidentally, xe2x80x9csemiconductor devicexe2x80x9d in the specification designates all of devices which function by utilizing a semiconductor and the followings are included in the category of a semiconductor device.
(1) Single element of TFT (Thin Film Transistor), IGFET (Insulated Gate Field Effect Transistor) or the like:
(2) Semiconductor circuit using the single element of (1):
(3) Electrooptical device constituted by (1), (2):
(4) Electronic device having (2), (3).
2. Description of Related Art
In recent years, a technology of constituting a thin film transistor (TFT) by using a semiconductor thin film (thickness; about several hundreds through several thousands xc3x85) formed on a substrate having an insulating surface has attracted attention. A thin film transistor is widely applied to electronic devices such as IC (Integrated Circuit) or an electrooptical device and particularly, development thereof has been accelerated as a switching element of an image display device.
For example, trials have been carried out in respect of applying TFT to all the electric circuits of a pixel matrix circuit for individually controlling pixel regions arranged in a matrix in a liquid crystal display device, a drive circuit for controlling the pixel matrix circuit, a logic circuit (processor circuit or memory circuit or the like) for processing data signal from outside and the like.
In the current state, TFT using an amorphous silicon film as an activation layer has been reduced into practice. However, in an electric circuit where high speed operational function is requested such as a drive circuit, a logic circuit or the like, TFT using a crystal silicon film (polysilicon film, polycrystal silicon film or the like) is needed.
For example, as a method of forming a crystalline silicon film on a glass substrate, a technology disclosed in Japanese Unexamined Patent Publication No. JP-A-7-130652 and a technology disclosed in Japanese Unexamined Patent Publication No. JP-A-8-78329 by the applicant have publicly been known. According to the technologies disclosed in these publications, a crystal silicon film having excellent crystalline performance can be formed by a heating treatment at 500 through 600xc2x0 C. for about 4 hrs by utilizing a catalyst element helping crystalize an amorphous silicon film.
Particularly, according to the technology disclosed in Japanese Unexamined Patent Publication No. JP-A-8-78329, crystal growth substantially parallel with a substrate face is carried out by applying the above-described technology and the inventors refer the formed crystallized region particularly as a horizontal growth region (or lateral growth region).
However, even when a drive circuit is constituted by using such a TFT, the required function cannot completely be satisfied yet. It is the current state that a high speed logic circuit requiring an extremely high speed operation of mega bit through giga bit level cannot be constituted by conventional TFT.
It is a problem of the present invention to provide a semiconductor device having extremely high function capable of constituting a high speed logic circuit which could not be fabricated by conventional TFT. Further, it is a problem of the present invention to provide a semiconductor thin film for realizing such a semiconductor device.
A semiconductor thin film provided by the present invention is featured in that the semiconductor thin film is provided with at least two crystals and grain boundaries among the crystals and a rate of incommensurate bonds to all of bonds at the grain boundaries is 5% or lower (preferably, 3% or lower).
As another constitution, the semiconductor thin film according to the present invention is featured in that the semiconductor thin film is provided with at least two crystals and grain boundaries among crystals and a number of incommensurate bonds included in 100 of bonds is 5 or smaller (preferably, 3 or smaller) at least in one arbitrary region of the crystal boundaries.
As another constitution, the semiconductor thin film provided by the present invention is featured in that the semiconductor thin film is provided with at least two crystals and grain boundaries among crystals and a number of incommensurate bonds included in 50 of bonds is 0 at least in one arbitrary region of the crystal boundaries.
As another constitution, the semiconductor thin film of the present invention is featured in that the semiconductor thin film is provided with at least two crystals and grain boundaries among crystals and an angle made by a lattice striation observed in an arbitrary one of the at least two crystals and a lattice striation observed in a contiguous other one of the two crystals falls in a range of 60 through 80xc2x0.
The present invention constitutes an activation layer of a semiconductor device represented by TFT by using a semiconductor film constituted as described above and a semiconductor device having high function sufficient for constituting a drive circuit or a logic circuit is realized.
A detailed explanation will be given of the constitution of the present invention described above by embodiments described in the following.